1. Field of the Invention
The invention is concerned with a hydraulic motor and a control system therefor and more particularly with improvements in the control system which allow the hydraulic motor to operate in any of a Neutral (Hold), Float, Raise or Lower position. Such a control system is particularly advantageous when used with various types of earth working equipment such as, for example, a front loading loader, a lift piston of a tractor-scraper, a dozer and the like.
2. Prior Art
Control valves for hydraulic motors are known which provide Float, Neutral, Raise and Lower positions. Further, a particular safety problem exists with prior art hydraulic motors control systems, which problem is that the pressure from the pump to the hydraulic motor of such a system may be suddenly cut off during Raise or Neutral operation due to the breakage of the line therebetween, failure of the pump, or failure of the engine driving the pump. In such an instance and particularly in cases of line breakage, if the hydraulic motor was holding a load in a Raised position, the load can fall very quickly under the influence of gravity thus causing potentially great harm to the load itself and to the equipment.
The present invention provides a particular control system-hydraulic motor combination which eliminates this problem of a fast falling load, but at the same time retains each of the Float, Neutral (or Hold), Lower and Raise positions of opertaion for the control system and which further operates solely by mechanical means thus providing quick and positive action and shifting between the Float position, the Neutral position, the Raise position and the Lower position.